Question

When you take cells or tissue pieces and grind them with an acid in a mortar and pestle, all the small molecules dissolve in the acid. Proteins, polysaccharides and nucleic acids are insoluble in mineral acid and get precipitated. The acid-soluble compounds include amino acids, nucleosides, small sugars etc. When one adds a phosphate group to a nucleoside, one gets another acid-soluble molecule called

• A. Adenine
• B. Nucleotide
• C. Nitrogen base
• D. Sugar phosphate

Answer 1

The correct option is B Nucleotide

Nitrogenous base

Nitrogenous base (purine/ pyrimidine) is a part of the nucleotide. Adenine, guanine are purines and cytosine, thymine, uracil are pyrimidines.

Nucleoside

The nitrogenous base combines with pentose sugar (ribose or deoxyribose) by a glycosidic bond to form a structure called nucleoside. Nucleoside does not have a phosphate group.

Nucleotide

The addition of a phosphate group to the nucleoside by phosphoester bond forms a nucleotide. Hence, a nucleotide contains three components:

1. Nitrogenous base
2. Pentose sugar: Ribose or deoxyribose
3. Phosphate group

Sugar phosphate

Sugar phosphate refers to the backbone formed in case of polynucleotides when the nucleotides are linked together.

Final answer: d. Nucleotide